I think you're harsh on Nadal, because Australian Open is a tough place to win, and when he won 2009 AO took a lot out of him physically. You're equating a small Rotterdam to the AO in terms of meaningful event, but that doesn't take away how hard it is to win. AO arguably the hardest of all the 4 slam, it's taxing on the body, and dealing with the heat wave. Basically, Nadal did something special that he doesn't deserve, because Borg didn't play back then. Could Borg have won the AO had he played? Maybe he could, but still the AO is no where near as competitive as today(as you stated that it wasn't meaningful). Nadal face all adversity in 2009, I'm not sure if Borg could've done given a same exact situation.

With that being said, if Nadal's AO win isn't the standard hold against Borg, some people shouldn't take Laver's 69 GS and hold against Federer and modern players, because it isn't applicable to today either. But somehow Federer always get slighted because he can't win the GS. It's a double standard.

No I'm not equating Rotterdam to the Australian Open in Nadal's time. I'm equating Rotterdam now to the Australian Open in Borg's time. There's a big difference there.

Imagine now if there was a slam that offered considerably less ranking points and prize money than the other 3 majors (and many non-slam tournaments for that matter), had absolutely terrible facilities, and was held at such an inconvenient time (so close to Christmas and for several years so soon before the more important Masters event). There would be withdrawals left, right and centre. That was the situation with the Aussie Open in Borg's time. Player's ranked outside the top 200 were getting direct entries into the Aussie Open during the mid to late 70s (despite the fact that it had a significantly smaller draw size to the other majors).

So using the Australian Open as some sort of yardstick when discussing Borg's career is stupid, as that ignores the context of his era. And yes many historians make an equally big mistake and judge Federer based on 60s and 70s standards (comparing Laver's overall title count to Federer's for instance is a utterly stupid).

Borg's career needs to be judged on the context of his era, i.e. when non-slam and invitational events were very lucrative and hence very important, when absolutely nobody cared about the grand slam title count including the players themselves, when there were only 3 proper majors a year, when the Masters and WCT Finals were hugely important tournaments etc.

Federer and Nadal's careers needs to be judged on the context of their eras, i.e. when grand slam counting is very important, when there are 4 equally important majors a year, when the non-slam events don't mean so much any more etc.

The players from the 70s and 80s like Borg and Connors probably get the worst deal. Some older historians judge them based on the context of the 60s Laver/Rosewall era and even previous eras, while some younger tennis fans judge them based on the context of the Sampras/Federer 90s and 00s era. i.e. looking at slams and nothing else. They are pretty much stuck in the middle.